Vehicular networks provide communications between vehicles. However, the network is exposed to a number of threats or attacks which may originate from various sources having different motivations. The network attacks may include a computer virus which attacks network communications. Also, network attacks may include attacks on privacy and malicious behavior attacks such as spam. Previous attempts to provide security for vehicular networks have relied on constant communication with road-side devices acting as servers providing a public-key infrastructure (PKI). Typically, previous solutions either did not consider the role of multiple, distributed, servers in a PKI for a vehicular network, or made unrealistic assumptions about the number of such servers, for instance, by considering the presence of a server in the wireless radio range of each vehicle. Thus, known security solutions for vehicular networks have ignored the problem of eliminating or minimizing the need for various types of costly infrastructure servers. In particular, conventional PKIs typically rely on trusted Certificate Authorities (CAs) or servers for the management of the cryptographic keys (used for public-key encryption or digital signatures) held by the users or clients that are authorized to belong to the PKI. Using a certificate, a trusted CA binds a cryptographic key to a specific user so that other users, by reading the certificate, can verify that a given key belongs to a given PKI user. The CA can exclude from the group any PKI user that exhibits malicious behavior by posting this user's certificate on a Certificate Revocation List (CRL) that is publicly available. Thus, other users, by obtaining the latest CRL from the CA, can verify that a given key belongs to a PKI user whose group membership privileges have not been revoked. Another reason that users need to communicate with the CA is to renew the certificates as these are typically time-limited (to avoid that CRL becoming too large in size). Realizing this communication between CA and PKI users becomes especially difficult in vehicular networks, where vehicles move across a wide geographic area but, due to their limited radio range, can only send messages for short distances. Therefore, the application of PKIs in a vehicular network with moving vehicles results in at least the problem of connecting and maintaining contact with CA servers across a wide geographic area, which may result in a solution of demanding an unreasonably high number of CA servers.
Message security refers to message authentication or integrity protection, and protection against replay attacks. In a distributed, group-based, setting such as a vehicular network, message security may also require authenticating a message as being originated by an authorized group member (i.e., for example, an authorized vehicle instead of an unauthorized computer). Known techniques for achieving message security are based on PKIs and digital signatures. Specifically, a user sends a digital signature of a time-stamped version of the current message together with the message itself and the certificate for the signature verification public key. The receiver checks that the time-stamp, the message's signature and the verification public key's certificate are valid before processing the message's content. This solution assumes the existence of constant availability of network connectivity to a Certificate Authority server infrastructure (to verify, as mentioned before, that the certificate used has not expired) and could also result in excessive computation time and over-the-air message overhead. Computationally lighter variants of this technique may include, for example, a user can check a message's authenticity only if the message's content is deemed to be important enough. Some known variations of this technique try to improve the computational efficiency by implementing signatures using chain-based or tree-based cryptographic hashing, however, this implementation decreases the communication efficiency. Even these variations assume the existence of constantly available network connectivity to the CA and also need the ability to maintain synchronization between sender and receivers. The simple approach of the CA distributing the CRL to all users at a given time t does not provide the desired security as at a later time t′>t, because a user may not be able to communicate to a CA server and thus may have to trust an old (and not updated) CRL.
Typical known methods and systems provide security options for users continuously connected to servers or common communication devices. However, known methods have not addressed, and are not generally suited for, providing security to users using mobile, decentralized communication systems, for example, as in vehicle to vehicle networks. Known networks have not addressed the challenges presented by mobile devices, such as in vehicle to vehicle networks, including their intrinsically mobile and ad-hoc nature, and their simultaneous needs for security and vehicle owner privacy.
It would therefore be desirable to provide a method and system for providing security for a vehicular network. It would further be desirable for a network system to provide security with a limited number of servers, while maintaining network parameters including desired security, privacy, and performance requirements.